The present invention relates to a network system for interconnecting a plurality of local area networks (LANs), and more particularly to a system suitable for rapidly and efficiently switching data between LANs.
In the past, discussion about a high speed interconnection unit for a plurality of LANs has been made on a bridge of a connection system for a MAC (media access control) layer which is a sublayer of an OSI (open systems interconnection) reference model in the 802.1 Committee which is one of the IEEE LAN standardization committees.
Application of relay path designation information to a transmission frame by a transmission terminal done to attain high speed relaying of a communication frame, error detection in the designation information and a logical protocol stack of a bridge are disclosed in JP-A-No. 60-264142 and JP-A-No. 60-264143 corresponding as filed by priority documents to U.S. application Ser. Nos. 616,742 and 616,743, respectively, each filed on June 4, 1984.
A high speed packet switching system is discussed in "PARIS: An Approach to Integrated Private Networks" Israel Cidon et al, IEEE, ICC 1987, 22.1.1-1.5. Technique for high speed relaying is based on the same concept as that of the path designation method disclosed in JP-A-60-264142.
A conventional cell switching system for switching a fixed length packet or cell is discussed in "PRELUDE: An Asynchronous Time-Division Switched Network" by Jean-Pierre Condreuse et al, ICC '87 22.2.1-22.2.6.
The bridge which is the MAC (media access control) layer interconnection relates to interconnection technique where a plurality of LANs to be interconnected are located in a relatively short distance. Each bridge is directly connected to the LAN without intervention of another network for connection.
On the other hand, the relay path designation system which imparts path information to all data frames can accelerate the relaying of the frames but it poses problems of reduction of an occupancy rate of information to be transmitted in the data frame and the necessity of preparation of the relay path at the terminal station at which the data frame is generated.